Ordinarily, a cop obtained from a spinning process is rewound in an automatic winder, and defects of yarns of the cop, such as neps or slubs, are cut and removed and yarn is wound in a package having a yarn quantity and shape (cheese or cone) suitable for the subsequent processing.
More specifically, the yarn taken out from the cop is passed through a tension device and a slub catcher and is wound on a package rotated by surface contact with a traversing drum while being traversed to the left and right, and when the yarn length or package diameter is increased to a predetermined value, the traversing drum is stopped and a full package is doffed automatically or by a worker.
Ordinarily, a switch for rotating the drum is turned off when full winding is sensed and simultaneously, a signal to the slub catcher is blocked. However, even if the switch for rotating the drum is turned off, the drum is not immediately stopped but is rotated at a frictionally decreasing speed by inertia. Accordingly, the drum finally stops after a certain time has passed from turning-off of the switch.
Even during this inertia rotation, so far as the yarn is left on the cop, the yarn is taken out from the cop, and the operation of winding the yarn on the package is continued. However, since the slub catcher and cutter are not actuated during this period, even if a slub is detected in the yarn wound by inertia rotation, the slub is not cut off and incorporation of defective yarn in the package occurs.
When the yarn speed during the ordinary winding operation is, for example, 2000 m/min, the length of the yarn wound by inertia rotation is generally about 100 mm, and incorporation of defective yarn onto the package cannot be avoided if such yarn passes during the inertia rotation period.
In conventional use, the slub catcher includes a device for detecting the presence or absence of the running yarn, and when the yarn is cut on detection of a slub, or when the running yarn is absent for other causes such as breakage, the device senses a yarn breakage condition and a knotting or splicing operation is carried out. However, since the slub catcher is deactivated on receipt of a signal indicating full winding of the package, the knotting operation is also inhibited and an absence of running yarn, caused by consumption of the yarn on the cop during the inertia rotation period, is not sensed. The yarn end is wound onto the package and there is no yarn between the cop and the package. In terms of control indications available, this condition appears identical to the condition of a yarn breakage or an unsuccessful knotting operation. Accordingly, the doffing operation, which includes capture of the yarn end between the cop and the package to start a new package winding operation, becomes difficult. In the alternative, an automatic doffing apparatus is not actuated and the doffing operation is not performed without manual intervention. In other words, at the doffing step, it is highly preferable that the yarn should be continuous between the cop and the package.